AS9618 TCN catv-tokushima

AS9618 (TCN) is held by Cable Television Tokushima (ケーブルテレビ徳島株式会社), known on air as Television Tokushima. It is the largest cable operator in Tokushima Prefecture on Shikoku, and has been a subsidiary of Shikoku Electric Power since 2006. The registry handle catv-tokushima says exactly what it is.

What it's used for

A small regional cable ISP. The AS announces just two IPv4 prefixes, 203.110.96.0/19 and 211.19.160.0/19, for 16,384 addresses in total, plus one IPv6 /32 (2404:2680::/32). The reverse DNS confirms the role directly: sampled addresses come back as usr203110096005.tcn.ne.jp and usr211019176005.tcn.ne.jp, where the usr prefix and the IP encoded straight into the hostname are the standard way a cable operator names its subscriber pool. One sampled address resolves to login.tcn.ne.jp, an operator-side service host rather than a customer line. The single observed BGP neighbour rules out any transit or peering role: this AS sits behind one upstream and exists to give the operator's own cable subscribers addresses.

Notable

• Two clean /19s and nothing else is unusually tidy for a network of this age. Most regional Japanese cable ISPs of comparable size have accreted a dozen or more scattered blocks.
• IPv6 is deployed as a full /32 despite the tiny IPv4 footprint, so the operator's addressing plan has room far beyond its current subscriber base.
• The operator is not independent: it became a subsidiary of Shikoku Electric Power, the regional electric utility, in 2006. The AS is still registered under the cable brand.